Journal of Plant Pathology Archive

Abstract:

In September 2012, cankers on branches and blighted fruit of pistachio (Pistacia vera) trees were observed in Arizona (USA). Infected fruit became dark brown to black, covered by small pycnidia, and rachises were dried up. Sometimes, dark discolored cankers extended from killed panicles to the sustaining shoot. A pycnidial fungus was consistently isolated from branch cankers and fruits and identified as Phoma fungicola Aveskamp, Gruyter et Verkley, based on morphological characteristics (Aveskamp et al., 2010) and analyses of the ITS and β-tubulin (BT) gene regions. The sequence showed high identity (ITS, 99%; BT, 99%) with a reference sequence (isolate CBS 633.92; accession Nos.: ITS, GU237900; BT, GU237609) for P. fungicola (Aveskamp et al., 2010). Sequences were deposited to GenBank (isolates: 7F90, 7F91 and 7F92. Accession Nos.: ITS, KC357253–KC357255; BT2, KC357256–KC357258; TEF-1α, KC357259– KC357261). Pathogenicity of P. fungicola to P. vera cvs Kerman and Peters was tested by inoculating isolates 7F90, 7F91 and 7F92 on 10 two-year-old branches per isolate. Inoculations were made in late October 2012 as described by Moral et al. (2010). Lesion length was measured 3 weeks after inoculation. The average lesion produced by isolates 7F90, 7F91 and 7F92 on cv. Kerman was 46.5, 57.5, 53.7 mm, and on cv. Peters was 45.0, 44.5, 49.5 mm in length, respectively. All lesions were significantly longer than those on the controls (average length 10.0 mm on two cultivars) (P <0.05). P. fungicola was re- isolated from the inoculated but not from the control branches. Results in this study indicate P. fungicola is a pathogen of pistachio branches and clusters. To our knowledge, this is the first report worldwide of P. fungicola attacking pistachio trees.